Texture of an object unexpectedly stretched
You have to UV unwrap it. Enter Edit mode, select the face, hit U, unwrap, this should fix the stretching.

Basically your texture is not correctly 'mapped' to your geometry. For a square face you want it to be square in UV space as well, here it most likely more of a rectangular shape.

Edit:
Your textures coordinates weren't correctly UV mapped, textures were projected based on your object bounding box (it's called 'generated', that's what blender does by default since it doesn't know how you want to project your textures). This is why you need to unwrap the face as described earlier and make sure you feed your noise textures vector inputs with proper data like so: